Merge "API extensions and sample app for spacial scalable encoder"

diff --cc vp8/vp8_cx_iface.c
Simple merge

diff --cc vp9/common/vp9_onyx.h
Simple merge

diff --cc vp9/encoder/vp9_onyx_if.c
Simple merge

diff --cc vp9/encoder/vp9_rdopt.c
Simple merge

diff --cc vp9/vp9_cx_iface.c
Simple merge

diff --cc vpx/vpx_encoder.h
Simple merge